In most prior art aircraft ECS's, mid and last stage bleed-air ports are provided on the engine compressor for provision of bleed air, or cabin compressors are driven mechanically by engine gear boxes. In the increasing drive to achieve energy-efficient engines, bleeding the engine compressor airflow impacts unfavorably upon the thermodynamic cycle of the engine and results in it being a very inefficient method of power extraction. This problem is further exacerbated by the trend toward high compression ratio engines. In contrast, the extraction of mechanical power has much less impact upon the thrust losses and upon the specific fuel consumption (SFC) of the new and advanced technology engines. Examples of aircraft air-conditioning and ECS's utilizing aircraft engine driven compressors can be found in U.S. Pat. Nos. 2,451,280 to Del Mar, 2,452,704 to Wahlmark, 2,585,570 to Messinger et al, 2,614,815 to Marchant et al, 2,678,542 to Stanton and 2,697,917 to Mayer.
Some of the problems often associated with prior art bleed air ECS's are: (1) the engine is subject to thrust loss and SFC penalties by bleeding the compressor; (2) pressurized (high temperature) air ducts must be routed up through the pylons and through the wings into the cabin; (3) failures of ducts can occur; (4) air ducts must be disconnected for engine removals; and (5) crossbleed-ducts are necessary to permit engine "cross-starts". On the other hand, mechanical compressors are: (1) bulky, noisy and create space problems around the accessory gear boxes; (2) inlet ducts and pressure ducts crowd the engine cowl; (3) mechanical compressors are high speed and require disconnect couplings; and (4) reliability is not good.
Electro-mechanical systems for extracting ECS power from aircraft engines offer yet another alternative. Such systems are disclosed in copending U.S. patent application Ser. Nos. 183,499, filed Sept. 2, 1980, for "ECS Energy Recovery System For Fuel-Efficient Aircraft", 183,609, filed Sept. 2, 1980, for "All Electric Environmental Control System For Advanced Transport Aircraft", and 183,079, filed Sept. 2, 1979, for "Direct-Driven Generator System for Environmental Control System and Engine Starting", all assigned to the assignee herein. All of the aforementioned applications, the disclosures of which are incorporated by reference herein, disclose ECS embodiments which include a compressor driven by an electric motor which derives its power from an engine-driven generator.
The aforementioned prior art patents and copending applications, incorporated herein by reference, all disclose systems which, to varying degrees of efficiency, carry out certain aircraft ECS and air-conditioning system functions. While the aforementioned copending applications disclose certain relatively high efficiency approaches to providing aircraft environmental control, it is nevertheless, an ongoing goal that ECS and air-conditioning systems be optimized in terms of efficiency in view of the present day strong need for fuel-efficient air transports. It is essential, then, that the energy and fuel consumption in extracting power for aircraft ECS's and air-conditioning systems be optimized (minimized).
Thus, it is a primary object of this invention to provide a method and system for optimizing aircraft ECS's in terms of energy, and thus, fuel consumption.
It is another object of this invention to provide an energy-efficient ECS system for aircraft which optimized the aircraft's fuel efficiency while providing conditioned air by extracting power from the aircraft's engines electromechanically.
It is another object of the present invention to provide an ECS and air conditioning system which efficiently extracts power electro-mechanically from an aircraft's engines while utilizing a single motor to drive two optimally designed compressors, a Freon compressor for air-conditioning and a cabin compressor for cabin air supply and pressurization needs.